Pneumatically controllable cowling



June 24, 1941. c. F. BLANDING 2,245,493

PNE UMATICALLY CONTROLLABLE COWLING Filed Dec. 22, 1939 INVENTOR CLA IEE/VC E E BLANDING BY ATTORN Patented June 24, 1941 UNITED STATES PATENT OFFICE PNEUMATICALLY CONTROLLABLE GOWLING Clarence F. Blanding, Arlington, Va. Application December 22, 1939, Serial No. 310,572 4 Claims. -(01. 123-471) (Granted under the act of March 3, 1883, as

1 amended April 30, 1 928; 370 0. 757) This invention relates to a pneumatically controllable cowling, and has for an object the provision of pneumatic means for controlling the cowling on anair cooled aircraft power plant.

This invention has all the advantages present in a mechanically controllable cowling such as is disclosed in the patents to Chilton, 2,158,273, May 16, 1939; Browne, 2,158,270, May 16, 1939; Adams, 2,150,143, March 14, 1939, and others, but avoids the disadvantages inherently present in any mechanically controllable cowling.

In addition to the advantages and purposesset forth in each of the above patents, the pneumatically controllable cowling of this invention has amongst its further advantages the possibility of being automatically controllable by the engine itself, according to the temperature conditions of the engine, and may beset to respond directly to the engine temperature or indirectly thereto by responding to a differential in pressure between thefront and rear of the engine.

cylinders, which has been found by experience to closely approximate temperature variations in the engine.

A further advantage of this invention is that a much simpler and less complicated system is provided by the present pneumatically controllable cowling than is possible with the conventional mechanically controllable cowling requiring a complicated systemof levers, rods and bell cranks for the interconnection and operation of the cowling, together with theheavy weight and high cost thereof as contrasted with the lower weight and lower cost of the present improved pneumatically controllable cowling.

Further advantages of the pneumatically controllable cowling when used on fighting planes as compared with the mechanically controllable cowling is that in the case of a mechanically controllable cowling a bulletrnight damage the control while it is in closed position, making it impossible to operate it from that position, so that the full power of the engine could not be used without danger of overheating and consequent failure. With the pneumatically controllable cowling of the present invention a bullet could injure the same only by puncturing the controlling mechanism, which would'result in the depletion of the pneumatic tube and consequently would open the exit to the maximurnwidth, thereby permitting the engine to be operated at full power without possibility of overheating.

With the foregoing and other objects in view,

the invention consists in the construction, combination and arrangement of parts hereinafter described and illustrated in the drawing, in which: i l

Fig.1 is a partly sectional, partly elevational view of a manually operable form of the pneumatically' controllable cowlingof this invention;

Fig.. 2 is a similar view of another form, operable according to engine temperature; and

Fig. 3 is a similar View of still another form, operable according to a pressure differential fore and aft of the engine.

There is shown at Ill a radial cylinder air cooled engine having the usual propeller H and engine cylinders 12 and mounted in the conventional manner within a nacelle skin l6 forwardly of the bulkhead or fire wall 13. This term nacelle means any engine embracing mount ing means, and may be the front portion of the fuselage, if the engine be mounted therein, or may be a separate engine mounting means located on a wing or elsewhere. Embracing the engine proper is an annular cowling I4 so shaped as to define a forward air entrance [5. At its rear edge I! anair exit or gill I8 is defined between such rear edge, and the joining edge 20 which is located between angular extension 2| of the bulkhead l3 and the fuselageor nacelle skin l6.

Mounted on this bulkhead extension 21 is a pneumatic tube 22 so located on the bulkhead extension 2| that when the tube 22 is inflated to the position shown in full lines it cuts the air exit or gill l8 to the minimum opening desirable, while when this pneumatic tube 22is completely deflated to the position shown in dotted lines at 22, it provides the maximum desirable size of the air exit or gill l8. As will be observed, the tube 22 when in either fully inflated or deflated position or in any intermediate position, is entirely inside the cowl lines of the airplane,

thus never affecting the frontal area of the cowl the cooling air provides a minimum of turbulence in merging with the outside air stream, and thereby reduces the drag of the airplane. In

addition, this minimum of turbulence precludes the possibility of disturbances set up in the air flow over the airplane which might result in severe vibration of parts of the airplane, notably the tail surfaces.

The elastic pneumatic tube 22 has its inflation and deflation controlled by means of a pressure conduit 23 connected from any suitable source of pressure available for this purpose, such as the discharge from the vacuum pump, the engine manifold pressure, a carbon dioxide bottle, or any other suitable source. A controllable valve 24 is installed in the pressure conduit 23 by operation of which the pressure fluid is caused to enter or escape from the tube 22 to inflate it or deflate it as much as or as little as necessary to thereby close or open the air exit or gill l8 correspondingly.

The air valve 24, as shown in Fig. 1, may be located convenient to the pilot or engineer, either directly by being located in the pilot's cockpit or indirectly by having a suitable control therefor located in the pilots cockpit.

Instead of being manually controlled by the pilot, it may be easily adapted for an automatic control. In one form, as shown in Fig. 2, this automatic control is operated by the change in temperature of some point on the engine cylinder l2, such as the spark plug gasket 25. Ther- -mocoup1e wires 26 and 21, of dissimilar metals such as iron and copper, extend between the spark plug gasket 25 and a response mechanism 28 for operating the valve 24-. The electromotive force generated between the dissimilar wires 26 and 21 at the gasket 25 causes the response mechanism 28 to actuate the valve 24 in such a way that an increase in the temperature of the cylinder l2 at the spark plug gasket 25 causes pressure to be bled by the valve 24 from the tube 22, thus enlarging the exit air or gill opening l8, allowing more cooling air to flow over the cylinders and lower the temperature thereof. Conversely, a decrease in temperature at 25 would operate valve 24 to allow pressure to enter tube 22, expanding it and decreasing the air exit or gill l8, thus curtailing the amount of cooling air flowing over the cylinders and allowing the temperature of the cylinders to increase.

Obviously, the point 25 should be so located that the temperature thereat is representative of the temperatures of all points for which cooling is desired. It may be noted that it is the present practice to locate a thermocouple at the spark plug gasket of the hottest cylinder with the wire leads connected to a gauge to indicate the temperature at such gasket. By experimentation and assignment of the proper constants to the response mechanism 28 the temperature .at the point 25 may be made constant at any predetermined value. In practice, the value of the temperature at the point 25 will be slightly less than the maximum allowable continuous temperature as determined by the engine manufacturer. This means of automatic regulation of cooling air flow just described is one of many possible using temperature as the control factor. Another way of automatically controlling the regulation of the cooling air flow is shown in Fig. 3, and utilizes the pressure flow of the cooling air from fore to aft of the engine cylinders as the control factor. Small hollow tubes 30 and 31 are installed with their open ends 32 and 33 facing the cooling air stream, the open end 32 being forward of the cylinder, and the open end 33 being aft of the cylinder. These tubes 30 and 3| are connected to the response mechanism 35, which controls the valve 24 so that the cooling air pressure forward of the cylinder is impressed on one side of a diaphragm or Sylphon inside the response mechanism 35, while the pressure aft of the cylinder is impressed on the other side of the diaphragm or Sylphon. The position of the diaphragm or Sylphon thus actuated by cooling air pressure differential determines whether air will be supplied to the inflatable tube or bled from it. The mechanism operates to provide a constant pres sure differential of the cooling air across the cylinder I2 sufiicient for cooling the cylinder under the severest conditions of air temperature and power output. During ground operation or a climb when the forward speed of the airplane is low, and the cooling air pressure ahead of the cylinder correspondingly low, the response mechanism 35 operates to allow air to bleed from the inflatable tube 22, increasing the exit or gill opening 58' and increasing the pressure differential across the cylinder; conversely, in high speed flight, the high cooling air pressure ahead of the cylinder l2 causes the valve 24 to open, allowing air under pressure to enter the inflatable tube 22, expanding it, diminishing the exit or gill opening 18 and decreasing the pressure differential to the value required for satisfactory engine cooling. It will be noted that, while the scheme shown in Fig. 3 provides automatic regulation of pressure differential across the cylinder, the condition desired is automatic regulation of the cylinder temperature. However, it has been determined from experience that, within the normal range of cooling air temperatures encountered, the cooling of the cylinders is proportional to the pressure difierential of the cooling air. Also, there is established for nearly every aircraft engine, the minimum pressure differential of the cooling air required for adequate engine cooling.

Other modifications and changes in the number and arrangement of the parts may be made by those skilled in the art without departing from the nature of the invention, withinthe scope of what is hereinafter claimed,

The invention described herein may be manufactured and/or used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Having thus set forth and disclosed the nature of this invention what is claimed is: v

1. In an aircraft, a nacelle skin, a cowling positioned forwardly of said nacelle skin and having its trailing edge spaced from said nacelle skin to define an air exit passage therebetween, anair intake opening at the leading edge ofsaid cowling, an aircraft power plant, cooling means for said power plant within said cowling between said air intake and exit, and means for adjusting said air exit comprising a pneumatic expandable and contractable member housed within said cowling at said exit, said pneumatic memher being expandable to close said exit and collapsible to open said exit, whereby should said pneumatic member be punctured, said exit will be left opened.

2. In an aircraft, a nacelle skin, an annular cowling positioned forwardly of said nacelle skin and having its trailing edge spaced from said nacelle skin to define an annular air exit passage therebetween, an air intake opening at the leading edge of said cowling, an aircraft power plant; cooling means for said power plant within said cowling between said air intake and exit, and means for adjusting said air exit comprising a pneumatic expandable and contractable annular aasame leading edge oi said cowling, an aircrait power 1 plant, cooling means for said power plant 10-,

cated within said cowling between said air intake and exit, and means tor adjusting said air exit comprising a pneumatic expandable and contractable annular tube housed within said expandable to close said exit and collapsible to open said exit, whereby should said pneumatic cowling at said exit,.said pneumatic tube being tube be punctured, said exit will be left opened. 4. In an aircraft, a nacelle skin, an annular cowling positioned forwardly of said nacelle skin and having its trailing edge spaced from said nacelle skin to define an air exit passage therebetween, an air intake opening at the leading edge oi said cowling, an aircraft power plant, cooling means for said power plant located within said cowling between said air intake and exit, and means for adjusting said air exit comprising a pneumatic expandable and contractable annular tube housed within said cowling at said exit, and pneumatic control means therefor, said pneumatic tube being expandable 'to close said exit and collapsible to open said exit, whereby should said pneumatic tube or control means be punctured, said exit will be left opened.

. CLARENCE F. BLANDING. 

